Cobalt oxides have gained much attention due to their potential applications in numerous areas of science and technology. Recently, the applications of cobalt oxides have been extensively investigated in the fields of catalysis, solid-state gas sensors, magnetic materials, electrochromic devices, and high-temperature solar collectors (Seshadri, R. et al., Chem. Mater. 2005, 17, 834-838). These interesting properties of the cobalt oxides result from their unique electronic structures and surface characteristics.
Cobalt oxides have been used as oxidation catalysts in several chemical processes. The catalytic activity of the cobalt oxides depends on preparation conditions, surface structures, degree of crystallization, oxidation states, surface area, and so on. The surface structures and compositions of the cobalt oxides play important roles for catalysis applications. It is often observed that the catalytic reaction using cobalt oxide takes place at elevated temperatures due to the activation of the catalyst and the acceleration of the reaction.
It has been known that hydrogen gas is generated by hydrolysis of sodium borohydride in the aid of acid, transition metals, or their salts (Kaufam, C. M. and Sen, B., J. Chem. Soc. Dalton Trans. 1985, 307-313). U.S. Pat. No. 6,534,033 discloses that transition metal catalyst for hydrogen generation may be obtained from a stabilized metal borohydride solution. Those metal catalysts, such as ruthenium, rhodium, or cobalt metal supported on various substrates exhibited high activity for hydrogen generation. Other metal catalysts, including silver, iron, nickel, copper, and so on are often inactive or less active for hydrogen generation at room temperature based on unpublished tests. Some metal catalysts such as copper and nickel, showed more activity after they were heated in nitrogen at 600-800 degree C. In addition, usage of high performance metal catalyst, such as ruthenium, rhodium or platinum is cost prohibitive for one-time use in various applications.
According to a recent publication (Kojima, Y. et al., Int. J. Hydrogen Energy, 2002, 27, 1029-1034), Toyota Central R&D Laboratories, Inc. reported that a catalyst containing platinum and LiCoO2 has a high catalytic activity for hydrogen generation due to the synergistic effects of afinely divided platinum metal on the metal oxide framework. However, this system still uses a precious metal like platinum, which is not attractive for practical application due to high production cost. From a practical point of view, a high performance catalyst for hydrogen generation having low production cost is highly desirable.